Sectional garage doors typically include a counterbalance system that compensates for the weight of the garage door to require a substantially uniform force to move the door throughout its travel between a closed position and an open position, such that the door may be opened with ease and closed without slamming the door to the floor. Counterbalancing is commonly accomplished with extension or torsion springs that are coupled to the door, as by cables, during installation. Torsion springs are conventionally tensioned by winding. This operation is often performed manually, as by inserting winding bars into spring perches to effect rotation. As will be appreciated, this operation can be dangerous, and, thus, various devices have been designed to reduce the danger of tensioning the springs.
One known design employs a power tool having a rotatable drive member mounted on a casing carrying a power transmitting structure. The drive member has a slot with an open end for accommodating the shaft of the counterbalancing mechanism and a releasable coupling structure that connects the drive member with a collar attached to the counterbalance spring, such that rotation of the drive member applies a rotational force to the spring. In this way, a motor within the power transmitting structure is used to drive the collar and tension the spring. A socket or pipe adapter may be connected to the drive member to allow the power tool to rotate nuts, bolts and pipes. While this device can be provided to an installer for multiple uses and does not need to be shipped with each door, not all doors, such as do-it-yourself doors, are installed by a professional installer making this device expensive for a single use. The device is rather heavy and bulky and includes a significant number of components making it expensive to ship with each door, leaving the do-it-yourself consumer to manually tension the counterbalance spring.
Another known design consists of a collar that can be slipped over a rod around which the counterbalance spring is wound, fitted with a pair of ratcheting mechanisms and a device to hold the same in place while the ratchets are used. The device also includes a boss for hooking into the spring collar and applying the correct tension through the use of the ratcheting arrangement. Means for attaching the collar to one end of the spring are provided and, thus, the spring is tensioned through use of the ratcheting mechanism.
Another known device includes a tool for applying rotational force to a coiled torsion spring of a door counterbalancing mechanism. The tool includes a split housing fixedly mounted on the winding cone of the torsion spring. This housing has a sprocket mounted thereon. On either side of the sprocket are annular grooves that respectively connect to a right hand operated and left hand operated ratchet tool. These ratchet tools are to be used sequentially in unison to create tension within the spring.
Still another design is an arrangement for an overhead garage door that includes an adapter used for tensioning the coil spring. The adapter has a body that may be mounted on a rotatable shaft that supports the coil spring and be non-rotatably attached to the end of the coil spring and the rotatable shaft. The attachment to the shaft is a releasable connection and the body has splines or projecting abutment surfaces so that two wrenches may have their jaws closely surround and engage the splines on the body. The wrenches have releasable latches that are designed to engage and disengage the splines on the adapter body. To tension the door, the splines are engaged and rotated with the wrenches in an alternate manner.
With the previously discussed designs, it is not practical to ship the specialized tools with each door. Also, when performing maintenance on doors, these specialized tools may be lost and require replacement when the springs need retensioning. Also, excessive wear may make it impossible to use the specialized tools to retention the spring. As a further practical consideration, these tools are normally used when one is standing on a ladder and tools that are bulky or require two hands to operate make it difficult to maintain one's balance on a ladder, thereby resulting in a safety concern.
Another approach to tensioning such counterbalance systems contemplates a wormgear/worm reducer that allows use of an electric power tool, such as a drill motor, to adjust tension in the spring. Such devices are normally made integral with the counterbalance system. The cost of the winding components adds significantly to the overall cost of the door, thereby making the system more expensive than doors with conventional counterbalance systems. While these systems are very capable of tensioning the door, they lack the physical feedback of the door tension found in the manually operated devices. Consequently, such winding devices need a counter that indicates the applied or removed tension without adding significant cost to the door. As a further disadvantage, since these mechanisms are normally integral with the counterbalance system, they may not be used to tension different doors. Therefore, there is a further need for a system that may be used on many different doors.
One known example of a counterbalance mechanism having a worm-gear assembly for a sectional garage door includes an elongated shaft mounted above the door opening and supporting spaced apart cable drums connected to respective cables that transmit a counterbalance force to the door. Opposing torsion springs are connected to the cable drums at one end and hub members at the other end that are axially slidable but non-rotatable relative to the shaft. The drums are provided with detachable bushing members for engagement with support brackets. The shaft is connected to a non-reversible worm-gear drive at one end. The worm-gear drive may be actuated to selectively vary the torsional winding of the counterbalance springs by rotating the worm and ring gear meshing therewith. The worm-gear drive may be detachably mounted on one or other end of shaft support brackets and a lock plate is supported on the shaft and engagable with the bracket to prevent rotation of the shaft when the mechanism is removed. Spring biased rollers are provided to compensate for skewing of the door caused by the shaft loading both springs which do not have identical characteristics.
Yet another known worm-gear counterbalance system includes a tubular shaft mounted on wall brackets carrying spaced apart cable drums operable to wind counterbalance cables thereon and counterbalance the weight of the door. Torsion springs inner connect with the cable drums and a spring winder tube is sleeved over the springs and connected to the wall brackets by a winding mechanism. The winding mechanism includes a support plate having spaced apart tabs adapted to register in corresponding slots formed in the wall bracket. The winding mechanism further includes a worm-gear drive including a ring-gear which is connected to one end of the winder tube by arrangement of radially inward projecting key portions and a bore of the ring gear, which register with axial grooves formed in the winder tube and are adapted to slide into transverse slots intersecting the grooves. A removable lock pin is engagable with the ring-gear or the worm of the worm-gear drive.
In still another worm-gear counterbalance system design, similar to the previously described design, spring winding and protected cover tubes are sleeved over the springs and connect to support brackets by a worm-gear drive winding mechanism. The worm-gear drive winding mechanism rotates the tubes to effect winding of the torsion coil springs through hub assemblies but prevents rotation of the tubes during normal operation of the counterbalance system. The cable drums and spring hub assemblies may be supported on an elongated synchronizing shaft or torque transfer shaft extending between and supported on the wall brackets.